Fixed admindoc template errors introduced by 02fd87c821.

Also regenerated the affected translation template.

Refs #20540.
Switched to using some constants the hmac module exposes.
Added get_app_paths() to the AppCache.

This method is useful to discover files inside apps.
Fixed #20485 -- Refactored loaddata for speed.

Thanks Anssi for reporting this performance bottleneck.
Fixed #20552 -- Corrected release notes reference to name of new test discovery runner.
Fixed small regression from 51aa000378.

A test failed if the path to the Django checkout contained a dot.

Refs #20485.
Fixed loaddata for Django checkouts with non ASCII chars in the name.
Fixed #20545 - Made class-based view MRO lists consistent.

Thanks wim@ for the suggestion.
Fixed #20532 -- Reverse auth views by name, not by path.

Auth views should be reversed by name, not their locations in
`django.contrib.auth.views`. This allows substituting your own
implementations of the auth views.
Fixed #17601 -- expose underlying db exceptions under py2

Use __cause__ to expose the underlying database exceptions even
under python 2.
Merge pull request #1241 from jaylett/master

Explicit exception chaining for db exceptions by setting __cause__ in py2
Added i18n-related URL mapper test for a mailing list report.
Fixed #18924 -- Made test.Client.logout send user_logged_out signal.

Thanks awsum for the suggestion and Pavel Ponomarev and
Florian Hahn for the patch.
Fixed #17927 -- Added initial values support for BaseGenericInlineFormSet

Thanks Fak3 for the suggestion.
Proofed the 1.6 release notes
PEP 8 cleanup
Fixed #19080 -- Fine-grained control over select_related in admin
Fixed #20564 -- Generic relations exclude() regression

The patch for #19385 caused a regression in certain generic relations
.exclude() filters if a subquery was needed. The fix contains a
refactoring to how Query.split_exclude() and Query.trim_start()
interact.

Thanks to Trac alias nferrari for the report.
Merge pull request #1245 from oinopion/list_select_related

Fixed #19080 -- Fine-grained control over select_related in admin
Fixed #20502 (again) -- More i18n cache flush in tests

Thanks Timo Graham for noticing the failures.